Incorporating nanostructures in thin film solar cells is an interesting way to improve the optoelectronic performance of the device by means of light-trapping and light management. However, designing the optimal shape and dimensions of the nanostructure is of critical importance for enhanced device performance. It is desired to have synergistic effects in the optical and electronic domains to result in a better performance. However in some nanostructures, the geometrically induced effects in these two domains might counteract resulting in a relatively inferior performance in the nano-structured device. We show this with a simulated example of a nanostructured organic solar cell with nano-pillar transparent electrodes. Here it is seen that the enhancement in photocurrent due to nano-scale scattering through the walls of the pillar is suppressed by the steady-state potential distribution induced by the nano-scale geometry. As a result of poor charge separation in the regions around the pillar, the photocurrents decrease. It is thus highlighted that the opto-electronic transport and electric field enhancement based co-degisn of nanostructures is important to fully understand the nano-scale effects.